EAGER: Collaborative Research: Continental Subduction and Deep Crustal Melting

俯冲的大陆地壳可以达到许多地壳岩性的固相线以上的压力-温度条件，但地壳深部熔融的条件、时间和后果在很大程度上是未知的。虽然有超高压熔融的实验研究，但很少有基于现场的自然例子的研究；现有的工作主要集中在与超高压地体有关的花岗岩体的年龄和化学特征上，而不是对常见的超高压岩石所在的混合岩。俯冲过程中产生大量部分熔融的地壳，对于从地幔到地壳的质量和热传递、通过增加在深部产生的部分熔融物质的造山生长以及造山地貌的演化(例如高原的发展)具有重要意义。此外，在理解(U)高压岩石在折返和随后的造山过程中被叠加的机制时，必须考虑部分熔融地壳的作用。这项拟议的早期勘探研究补助金项目旨在从与榴辉岩空间相关的岩浆体(白云、伟晶岩)获得锆石U/Pb年龄，以确定锆石是否在超高压条件下结晶并因此发生熔融。如果这项探索性研究成功，它将为一个更大规模的项目奠定基础，最终目的是检验这一假设，即在某些造山带中，大陆地壳的部分熔融发生在大陆俯冲过程中，并与造山带的热机械演化和超高压岩石折返有动力学联系。寻找足够的样品将在西部片麻岩地区(挪威)进行，因为这是一个容易接近的地点，有大量出露的超高压岩石，这些岩石是混合岩的宿主；一些榴辉岩体本身就是混合岩。

Subducted continental crust can attain pressure-temperature conditions that are above the solidus for many crustal lithologies, but the conditions, timing, and consequences of deep crustal melting are largely unexplored. Although there have been experimental investigations of ultrahigh-pressure (UHP) melting, there are very few field-based studies of natural examples; existing work has focused largely on the age and chemical characteristics of granitoid bodies that are associated with UHP terrains and not on migmatites that commonly host UHP rocks. The generation of large amounts of partially molten crust during subduction has implications for mass and heat transfer from the mantle to the crust, orogenic growth by the addition of partially molten material generated at depth, and evolution of orogenic landscapes (e.g. development of plateaux). Moreover, the role of partially molten crust must be considered in understanding the mechanisms by which (U)HP rocks are overprinted during exhumation and subsequent orogenic processes. This proposed Early Grant for Exploratory Research (EAGER) project is designed to obtain U/Pb zircon ages from magma bodies (leucosomes, pegmatites) spatially associated with eclogite to determine if zircon crystallized and thus melting occurred at UHP conditions. If this exploratory study is successful, it will set up the background canvas for a larger scale project with the ultimate goal of testing the hypothesis that, in some orogens, partial melting of continental crust occurs during continental subduction and is dynamically linked to the thermal-mechanical evolution of orogens and the exhumation of UHP rocks. The pursuit for adequate sample material will take place in the Western Gneiss Region (Norway) because it is an accessible locale with abundant exposure of UHP rocks that are hosted by migmatite; some eclogite bodies are themselves migmatitic.